I. Field
The subject technology relates generally to communications systems and methods, and more particularly to systems and methods that employ power control components to mitigate interference between wireless cells and within a given cell.
II. Background
Wireless communications systems have been applied to almost every area of human interaction. From cell phones to text messaging systems, communications technology in this arena are constantly changing, improving, and evolving into other forms. One such technology includes the amount of digital data being employed such as Internet information that is now communicated to mobile wireless systems. Many systems currently deliver such digital information where there is a plurality of design standards to define how to deliver desired digital content to respective users. One such standard includes IEEE 802.20 that defines design guidelines for wireless systems that communicate various types of data.
In general, the guidelines set forth in 802.20 are intended as a specification for the PHY and MAC layers of an air interface for interoperable packet-data mobile broadband wireless access systems. Typically, such systems operate in licensed frequency bands below 3.5 GHz, support peak data rates per user in excess of 1 Mbps, support vehicular mobility classes up to 250 Km/h, and cover cell sizes commensurate with ubiquitous metropolitan area networks. This includes targeting spectral efficiencies that employ sustained user data rates with numbers of active users significantly higher than achieved by existing mobile systems.
Other features of 802.20 include the enablement for worldwide deployment of cost effective, spectrum efficient, always on and interoperable mobile broadband wireless access systems in order to address various user needs. These needs include mobile and ubiquitous Internet access, transparent support of Internet applications, access to enterprise intranet services, along with transparent access to infotainment and location services. Thus, the 802.20 specification fills the performance gap between high data-rate low mobility services currently developed in general 802 specifications and high mobility cellular networks.
The technical feasibility of 802.20 wireless systems has been demonstrated by proprietary systems currently in deployment and trial. These systems use technological components in wide deployment today, such as modems, radios, antennas and PHY/MAC protocols. These solutions may use well understood spread spectrum technologies (such as frequency hopping), radio technologies (such as OFDM), advanced signal processing techniques (such as adaptive antennas) and cellular architectures. Also, these technologies have been successfully tested and deployed over the past and are finding increased usage in the LAN/MAN and Cellular environments, for example. Commercial deployment of cellular wireless networks in bands licensed for mobile services demonstrates that air interface support for high reliability networks is in fact suitable for commercial deployment.
One area of interest with current design standards such as 802.20 relates to how a given wireless cell communicates to user equipment or terminals within its cell and how one wireless cell may impact on one or more other cells. This includes how to specify the amount of interference that may be caused by one or more wireless terminals in the cell and the impact these terminals may have on other terminals operating in adjacent cells. In general, it is desirable to control the amount of power generated in any one cell to mitigate interference in other cells that are within a given proximity and how the cells may be impacted. Also, terminals within any given cell may impact other terminals within the same cell since it may not be possible to have perfect orthogonality within the cell thus causing some leakage or interference within the cell. Currently, one method proposed by 802.20 involves controlling the amount of power that is transmitted within the cell. This method involves controlling the relative power spectral density from user equipment within the cells. A problem with this method is that there no feedback or communications to determine whether there is an impact from one cell or another. Also, in addition to relative power spectral density controls there may be more effective methods to control the amount of interference between cells and/or the potential for interference within a given cell.